/Engine/Source/Developer/TextureFormat/Public/Interfaces/ITextureFormat.h
bInImageHasAlphaChannel is whether or not to treat the source image format as having an alpha channel, independent of whether or not it actually has one.
virtual EPixelFormat GetEncodedPixelFormat ( const [FTextureBuildSettings](API\Developer\TextureCompressor\FTextureBuildSettings) & InBuildSettings, bool bInImageHasAlphaChannel ) const